Energy-resolved electrospray mass spectrometry of diexo- norbornane and norbornene derivatives containing a fused, phenyl-substituted, 1,3-oxazine ring: competitive retro-Diels–Alder fragmentation processes

Abstract

The fragmentation behaviour of an organic ion depends on both the amount and the distribution of internal energy resulting from the ionisation process. Thus, investigations of the fragmentation pathways of complex ions can gain some advantage from energyresolved mass spectrometry (ERMS) techniques. These methods are able to establish a relationship between the internal energy level of a precursor ion of interest and the nature and extent of the generated fragment ions. In the present study, the competitive retro-Diels-Alder fragmentation processes from norbornane and norbornene ions linked to 1,3-oxazine moieties were examined by ERMS, using an electrospray ionisation source and in-source collisional activation.

Proposed mechanisms for the fragmentation of doubly allylic alkenamides (tingle compounds) by low energy collisional activation in a triple quadrupole mass spectrometer

“…A plot of collision energy versus relative intensity of selected fragment ions leads to the generation of breakdown curves [20]. Evaluation of these breakdown curves can provide information on fragmentation mechanisms such as distinguishing between competitive and consecutive fragmentation pathways, the stability of product ions, and identification of first and subsequent generation product ions [21][22][23][24][25][26]; identification of isomers and tautomers [27][28][29]; and development of library searchable MS/MS spectra [30,31]. Since the internal energy of the precursor ion is not rigorously known, breakdown curves provide a qualitative picture of a fragmentation mechanism.…”

Identification of position isomers by energy‐resolved mass spectrometry

“…A possible alternative to gain the structural characteristics of these isomers is the investigation of the fragmentation of their gas phase ions using energy‐resolved mass spectrometry (ERMS). The technique involves the collisional activation of the gas phase ions either at the interface of an electrospray ionization source or by means of an inert collision gas in tandem mass spectrometry . By using the low‐energy collisional activation and tandem mass spectrometry, one can control the amount of energy transferred in to an ion by varying the collision energy (CE) and accordingly the fragmentation rate.…”

“…By using the low‐energy collisional activation and tandem mass spectrometry, one can control the amount of energy transferred in to an ion by varying the collision energy (CE) and accordingly the fragmentation rate. The compound specific ERMS curves are therefore exploited by many authors for the characterization of position and stereo isomers and even for conformational analysis …”

A study of b1+H2O and b1-ions in the product ion spectra of dipeptides containing N-terminal basic amino acid residues

“…A plot of relative intensity versus collision energy of selected fragment ions leads to the generation of breakdown curves [1,2]. Evaluation of these breakdown curves can provide information on fragmentation mechanisms such as distinguishing between competitive and consecutive fragmentation pathways, the stability of product ions, and identification of first and subsequent generation product ions [3][4][5][6][7][8]; identification of isomers and tautomers [9 -11]; and development of library searchable product ion spectra [12,13]. Since the internal energy of the precursor ion is not rigorously known, breakdown curves provide a qualitative picture of a fragmentation mechanism.…”